Characterization of several ultraviolet–visible emission lines from a lead hollow-cathode lamp

Simons, J. W.; Palmer, Byron A.; Hof, Douglas E.; Oldenborg, Richard C.

doi:10.1364/josab.6.001097

Cited by 17 publications

(11 citation statements)

References 4 publications

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“…The lines of Li, Ba, and Pb have both hyperfine splitting and isotopic shifts. The lines of Li and Ba are included in the Gaia/ESO line list, while Pb is not, so for this element data from Simons et al (1989) was used.…”

Section: Abundancesmentioning

confidence: 99%

An Elemental Assay of Very, Extremely, and Ultra-Metal-Poor Stars

Hansen¹,

Hansen

Christlieb³

et al. 2015

ApJ

137

127

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We present a high-resolution elemental-abundance analysis for a sample of 23 very metal-poor (VMP; [Fe/H] < −2.0) stars, 12 of which are extremely metal-poor (EMP; [Fe/H] < −3.0), and 4 of which are ultra metal-poor (UMP; [Fe/H] < −4.0). These stars were targeted to explore differences in the abundance ratios for elements that constrain the possible astrophysical sites of element production, including Li, C, N, O, the α-elements, the iron-peak elements, and a number of neutron-capture elements. This sample substantially increases the number of known carbon-enhanced metal-poor (CEMP) and nitrogen-enhanced metal-poor (NEMP) stars -our program stars include eight that are considered "normal" metal-poor stars, six CEMP-no stars, five CEMP-s stars, two CEMP-r stars, and two CEMP-r/s stars. One of the CEMP-r stars and one of the CEMP-r/s stars are possible NEMP stars. We detect lithium for three of the six CEMP-no stars, all of which are Li-depleted with respect to the Spite plateau. The majority of the CEMP stars have [C/N] > 0. The stars with [C/N] < 0 suggest a larger degree of mixing; the few CEMP-no stars that exhibit this signature are only found at [Fe/H] < −3.4, a metallicity below which we also find the CEMP-no stars with large enhancements in Na, Mg, and Al. We confirm the existence of two plateaus in the absolute carbon abundances of CEMP stars, as suggested by Spite et al. We also present evidence for a "floor" in the absolute Ba abundances of CEMP-no stars at A(Ba) ∼ −2.0. 1 Based on observations made with the European Southern Observatory telescopes.enhanced metal-poor (CEMP) stars (Beers et al. 1992; Beers & Christlieb 2005; Norris et al. 2013b). This class comprises a number of sub-classes (originally defined by Beers & Christlieb 2005), based on the behavior of their neutron-capture elements:(1) CEMP-no stars, which exhibit no over-abundances of n-capture elements, (2) CEMP-s stars, which show n-capture over-abundances consistent with the slow neutron-capture process, (3) CEMP-r stars, with n-capture over-abundances associated with the rapid neutron-capture process, and (4) CEMP-r/s stars, which exhibit n-capture overabundances that suggest contribution from both the slow and rapid neutron-capture processes. Each of these subclasses appear to be associated with different elementproduction histories, thus their study provides insight into the variety of astrophysical sites in the early Galaxy that were primarily responsible for their origin. The CEMP-no stars are of special importance, as the preponderance of evidence points to their being associated with elemental-abundance patterns that were produced by the very first generation of massive stars (Norris et al. 2013b;Hansen et al. 2014;Maeder et al. 2014), thus they potentially provide a unique probe of the first mass function in the early universe along with providing information on the nucleosynthesis and properties of the first stars.In a previous paper, Hansen et al. (2014) (hereafter paper I) provided a detailed study of the elemental abundances f...

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Section: Abundancesmentioning

confidence: 99%

An Elemental Assay of Very, Extremely, and Ultra-Metal-Poor Stars

Hansen¹,

Hansen

Christlieb³

et al. 2015

ApJ

137

127

View full text Add to dashboard Cite

show abstract

“…The effects of hyperfine splitting and isotope shifts are included in the analysis, using McWilliam (1998) for Ba, Lawler et al (2001) for La, and Simons et al (1989) for Pb. Solar isotope ratios are assumed for Pb.…”

Section: Abundances Of Other Elementsmentioning

confidence: 99%

Carbon‐Enhanced Metal‐Poor Stars. III. Main‐Sequence Turnoff Stars from the SDSS SEGUE Sample1

Aoki

Beers

Sivarani

et al. 2008

ApJ

116

168

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The chemical compositions of seven CEMP turnoff stars are determined from high-resolution spectroscopy. Five are selected from the SDSS SEGUE sample of metal-poor stars. Another star chosen from the SDSS SEGUE sample has only a weak upper limit on its carbon abundance obtained from the high-resolution spectrum. The effective temperatures are all higher than 6000 K, while the metallicities, parameterized by ½Fe/H, are all below À2; the star with the lowest iron abundance has ½Fe/H ¼ À3:1. Six of our objects exhibit high abundance ratios of barium (½Ba/Fe > þ1), suggesting large contributions of the products of former AGB companions via mass transfer across binary systems. One star (SDSS 1707+58) exhibits rapid variation in radial velocity, a strong signature that it belongs to a close binary. Combining our results with previous studies provides a total of 20 CEMP main-sequence turnoff stars for which the abundances of carbon and at least some neutron-capture elements are determined. The ½C/H ratios for this sample of CEMP turnoff stars are generally higher than those of CEMP giants and their dispersion is also smaller. These results indicate that the carbon-enhanced material from the companion AGB star is preserved at the surface of turnoff stars with no significant dilution, counter to expectations if processes such as thermohaline mixing have operated in unevolved CEMP stars. In contrast to the behavior of ½C/H, a large dispersion in the observed ½Ba/H is found for the CEMP turnoff stars, suggesting that the efficiency of the s-process in very metal-poor AGB stars may differ greatly from star to star. Four of the six stars from the sample exhibit kinematics associated with membership in the outer-halo population, a remarkably high fraction.

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“…Figure 1 shows examples of the observed spectra, and the results of synthetic fits, for HD 196944 and CS 31062-050. In this analysis we adopted the line data for the hyperfine splitting and isotope shifts determined by Simons et al (1989), as given in Table 4. We found that the fit between the observed spectra and the calculated ones is better, when the absolute wavelength of the Pb lines are slightly shifted.…”

Section: Abundance Analysismentioning

confidence: 99%

“…We found that the fit between the observed spectra and the calculated ones is better, when the absolute wavelength of the Pb lines are slightly shifted. For this reason, we shifted the wavelength of these lines by 0.005 Å, which is as large as the uncertainty in the determination of the absolute line position by Simons et al (1989), in our spectrum synthesis. The CH 4057 Å line blending with the Pb I line was calculated for the carbon abundance which best reproduced other lines of the same CH band.…”

Section: Abundance Analysismentioning

confidence: 99%

A Subaru/High Dispersion Spectrograph Study of Lead (Pb) Abundances in Eights‐Process Element–rich, Metal‐poor Stars

Aoki

Ryan

Norris

et al. 2002

ApJ

191

243

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We report the abundances of neutron-capture elements in eight carbon-rich, metal-poor (À2:7 ½Fe=H À1:9) stars observed with the Subaru Telescope High Dispersion Spectrograph. The derived abundance patterns indicate that the neutron-capture elements in these objects primarily originated from s-process nucleosynthesis, although the [Ba/Eu] abundance ratios in some objects are lower than that of the solar system s-process component. The present analysis has yielded the Pb abundances for seven objects as well as an upper limit for one object from use of the Pb i 4057 and 3683 lines. The values of [Pb/ Ba] in these objects cover a wide range, between À0.3 and 1.2. Theoretical studies of s-process nucleosynthesis at low metallicity are required to explain this large dispersion of the [Pb/Ba] values. Variations in radial velocity have been found for two of the eight objects, suggesting that, at least in these instances, the observed excess of s-process elements is due to the transfer of material across a binary system including an AGB star. Comparisons with predictions of AGB nucleosynthesis models are discussed.

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Characterization of several ultraviolet–visible emission lines from a lead hollow-cathode lamp

Cited by 17 publications

References 4 publications

An Elemental Assay of Very, Extremely, and Ultra-Metal-Poor Stars

An Elemental Assay of Very, Extremely, and Ultra-Metal-Poor Stars

Carbon‐Enhanced Metal‐Poor Stars. III. Main‐Sequence Turnoff Stars from the SDSS SEGUE Sample1

A Subaru/High Dispersion Spectrograph Study of Lead (Pb) Abundances in Eights‐Process Element–rich, Metal‐poor Stars

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